Curvature measurement device

ABSTRACT

A curvature measurement device is described having an elongated flexible member with at least one sensing wire attached at one end of the flexible member and extending along said flexible member to the other end thereof. The flexible member is attached to an object whose curvature is to be measured and flexed in accordance with the shape of the object. A deviation sensing means coupled to the non-fixed end of the sensing wire measures the change in position of said wire as the flexible member is flexed to produce an electrical output signal proportional to the change in position.

United States Patent 11 1 Yoslow et a1.

1 1 Sept. 30, 1975 CURVATURE MEASUREMENT DEVICE [73] Assignee: WilmarkElectronic Co., lnc., New

York. NY.

221 Filed: Aug. 29, 1973 1211 ApplNo.:392.489

[52] US. Cl. 33/174 L; 128/2 S {51] Int. Cl. ..G01B 5/20 [58] Field ofSearch 33/147 D, 148 D, 175 DG, 33/179.172 E, 174 D, 174 R. 174 L. 174E.

80, DIG. 3; 128/2 S; 338/47 [56] References Cited UNITED STATES PATENTS2.324.672 7/1943 Bicrman et a1. 128/2 S 2,508,419 5/1950 Ramberg 33/DlG.13

3.293.585 12/1960 Horn 338/47 3,496,644 2/1970 Short...

9/1971 Hall 128/2 S Primary E.\'amiMerHarry N. Haroian Attorney. Age/1!.0r Firm-Friedman & Goodman [57] ABSTRACT A curvature measurement deviceis described having an elongated flexible member with at least onesensing wire attached at one end of the flexible member and extendingalong said flexible member to the other end thereof. The flexible memberis attached to an object whose curvature is to be measured and flexed inaccordance with the shape of the object. A deviation sensing meanscoupled to the non-fixed end of the sensing wire measures the change inposition of said wire as the flexible member is flexed to produce anelectrical output signal proportional to the change in position.

19 Claims, 15 Drawing Figures .U.S. Patent Sept. 30,1975 Sheet 1 of33,908,279

OUTPU Sl-GN A DEVIC TRANS- DUCE DEVIATION SENSING UNIT OUTPUT MODULEFIG.

4o FlG.2 FIG?) U.S. Patant Sept. 30,1975 Sheet20f3 3,908,279

OUTPUT E m F US. Patent Sept. 30,1975 Sheet 3 of 3 3,908,279

CURVATURE MEASUREMENT DEVICE BACKGROUND OF THE INVENTION This inventionrelates to a curvature measurement device, and more particularly to adevice which can measure the continuous angular curvature or rotationalcurvature of an object. The invention has particular but not exclusiveapplication to the measurement of the curvature of the human spine inconnection with correct posture detectors.

In numerous fields of industry such as the construction industry ormaterials testing industry it is necessary to measure the curvature of aparticular structural member, or to be able to continuously measurechanges in curvature of such structural members. Most state of the artmeasurement devices for this purpose utilize strain gauges wherein aparticular element such as a wire changes its dimension in accordancewith changes in the curvature of the element to be measured. Some straingauge devices utilize electrical resistance wires whose resistancechanges as the dimensions of the wire change due to curvature of theobject being measured. Other strain gauge devices utilize a wire inconjunction with a switch or other detecting element such that as thewire changes its dimensions in accordance with curvature of the elementto be measured, the detecting device is triggered to produce an outputsignal.

While these devices may be satisfactory for some purposes, theygenerally are expensive and complex because they require a special typeof strain gauge element which is sufficiently sensitive to producedetectible results from even slight curvatures.

A specific application of such curvature measurement devices finds usein connection with poor posture detectors which are placed on the backof a wearer and detect spinal curvature. It is well known thatmalposition of the human spinal column is the cause of many ailments.Such ailments, as well as discomfort, can be avoided with correctposture; however, a patient is generally not aware of his poor postureposition, By utilizing a curvature measurement device it is possible toprovide the patient with greater spinal curvature awareness than hecould achieve naturally.

One poor posture detector known in the art is described in US. Pat. No.3,608,541. This device utilizes a flexible column hinged at one sidethereof which has an actuating cable at the opposite side thereof whichactuates a switch when the column is flexed greater than a given presetamount. While this device eliminates the necessity for a strain gaugedetector it is not satisfactory for general spinal curvature awareness,since it cannot provide continuous signals proportional to any change inthe curvature. In addition, because of its special construction, it isinherently limited in use to spinal curvature detection rather thanindustrial use. Furthermore, since the detector is limited to the use ofone wire because of its peculiar construction, the device is notextremely sensitive and while it satisfies as a threshold detectiondevice it would not be adequate for a continuous signalling device.Still further, the detector described in the aforementioned patent canonly detect angular curvature in a given plane but can not detectrotational curvature about a given axis.

SUMMARY OF THE INVENTION It is therefore an object of this invention toprovide a curvature measurement device which avoids the aforementionedproblems of the prior art.

Still a further object of the invention is to provide a curvaturemeasurement device which can provide a continuous electrical outputsignal proportional to curvature changes in an object being measured.

Still another object of this invention is to provide a curvaturemeasurement device which can be utilized to measure angular curvature ina given plane and/or rotational curvature about a given axis.

Yet another object of this invention is to provide a curvature sensingdevice which senses curvature in an object being measured and providessignals to a deviation sensing device which produces an electricalsignal proportional to said curvature changes.

A further object of this invention is to provide a curvature measurementdevice which can be used as a poor posture detector providing continuousoutput signals proportional to the changes in curvature of the spine.

St ll another object of the invention is to provide a curvaturemeasurement device which can be preset to detect all changes incurvature from the preset position.

Still another object of the invention is to provide a curvaturemeasurement device which is simple in construction and easy to utilize.

These and other objects, features and advantages of the invention willin part, be pointed out with particularity, and will in part becomeobvious from the following more detailed description of the inventiontaken in conjunction with the accompanying drawings, which forms anintegral part thereof.

Briefly, this invention provides an elongated flexible member which canbe coupled to an object whose curvature is to be measured, such as forexample the spine of a patient. At least one sensing wire is fixedlyconnected to said flexible member at one location thereof, such as thebase end of the elongated flexible member. The sensing wire extendsalong the flexible member to another location thereof, such as forexample the opposite end of the elongated flexible member. As theflexible member flexes in accordance with a change in the curvature ofthe object to be measured, the sensing wire will change its positionrelative to the flexible member. A deviation sensing device located atthe unconnect ed end of the sensing wire can detect the change inposition of the sensing wire relative to the flexible member. Suchchange in position is converted into an electrical signal which will beproportional to the change in curvature.

In one embodiment of the invention two sensing wires are located oneither side of the elongated flexible member forming a single planewhich can detect curvature of the flexible member within that plane. Byutilizing four wires in two pairs, two different planes can beestablished and curvature of the flexible member within each plane canbe measured. By utilizing sensing wires which are spirally wound aboutthe flexible member rotational curvature about a central axis can bemeasured.

In one embodiment the deviation sensing device is a resistive collarhaving a voltage impressed across it and being fixed to one end of theelongated flexible member. The sensing wires terminate in sliding meanswhich can slide along the internal surface of the resistive collar. Thevoltage across the sensing wires is measured at the change in positionof the wire changes the resis tance of the bridge arms such that theamount of positional change in the wires can be measured.

BRIEF DESCRIPTION OF THE DRAWINGS With the above and additional objectsand advantages in view, as will hereinafter appear, this inventioncomprises the devices, combinations and arrangements of partshereinafter described and illustrated in the accompanying drawings of apreferred embodiment in which:

FIG. 1 is a block diagram showing the basic elements of the presentinvention as used in a complete measuring system;

FIG. 2 is a frontal isometric view of one embodiment of the measuringdevice of the present invention;

FIG. 3 is a sectional elevational view of the embodiment shown in FIG.2;

FIG. 4 is a schematic diagram useful in explaining the theory ofoperation of the present invention;

FIG. 5 is a frontal isometric and partly electrical schematic drawing ofanother embodiment of the present invention;

FIG. 6 is an electrical schematic drawing showing the equivalent of thedevice of FIG. 5;,

FIG. 7 is a sectional elevational and partly electrically schematicdrawing showing a further embodiment of the measuring device inaccordance with the present invention;

FIG. 8 is a fragmentary sectional elevational view of the embodimentshown in FIG. 5;

FIG. 9 is a fragmentary sectional elevational view of yet anotherembodiment of the measuring device in accordance with the presentinvention;

FIGS. 10, 11 and 12 are transverse sectional views showing various waysof retaining the wires to the flexible member in accordance with thepresent invention;

FIG. 13 is an elevational view of the sensing device wherein the wiresare spirally located relative to the flexible member;

FIG. 14 is an elevational view of a cascaded assembly in accordance withthe present invention; and

FIG. 15 is an isometric view of retaining means useful in accordancewith the measuring device of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1 thereis shown a general block diagram of the curvature measurement deviceincorporated within a measurement system in accordance with the presentinvention. There is included an input transducer 10 which is fastened tothe object whose curvature is to be measured, such as a patient's spine.The transducer can be fastened with conventional means such as tape,elastic belt, or in the case of industrial objects by means of bracedevices or other known means. The transducer provides an output which isa function of the curvature of the object being measured.

A deviation sensing unit 12 receives the output signal from thetransducer and calculates a deviation signal from a preset value. Byadjustment of the preset value through means 14, a zero signal can beobtained at any desired curvature. As the transducer is flexed to asmaller radius of curvature, that is to say more bending of the object,the deviation signal becomes proportionately larger.

An output signal device 15 receives the deviation signal and producesthe necessary conditioned output signal needed by the output module 16.The detailed circuitry of the output signal device 15 as well as theoutput module 16 will depend upon the type of output transducer used inconnection with the present invention. By way of example, the outputmodule can feed an audio system 18 wherein the tone, frequency oramplitude of the output audio signal is proportional to the deviationsignal produced. A visual system 20 can be utilized wherein a meter hasits output proportional to the deviation signal. Other types of visualsystems could be used wherein the color, amplitude or spacialorientation is proportional to the deviation signal. The output module16 could also feed into graphic devices 22 or computer devices where theoutput signal is registered in a computer memory for storage or furthercomputational use.

When utilizing the curvature measurement device of the present inventionas a poor posture detector, other types of output transducers could beused as well. For example, a skin stimulation system could be utilizedwherein the frequency or amplitude of the stimulation to the wearer isproportional to the deviation signal. Also, a direct muscle stimulationsystem could be utilized wherein the stimulation is proportional to thedeviation signal. Also, a pain stimulation system could be utilizedwhere the amount of pain stimulation to the wearer is directlyproportional to the deviation signal, which would then provide him witha reminder of the poor posture and encourage him to correct the spinalcurvature thereby improving his posture.

Referring now to FIG. 2 there is shown a transducer, shown generally at24 which includes a support member in the form of an elongated flexiblemember 26 which is shown provided with open longitudinal grooves 28, 30,32 and 34 about the periphery of the member 26. The member 26 may bemade from any suitable material which permits it to be flexed withoutbreaking. An example of such material is nylon.

Although four grooves in the form of two pairs of opposite grooves havebeen shown, the present invention can also be used with less than fourgrooves, as will become apparent hereafter.

In the embodiment shown, grooves 32 and 34 are utilized in whichrespective sensing wires 36 and 38 are disposed. The wires are fixedlycoupled to the flexible member at one location thereof. As can best beseen in FIG. 3, the wires 36 and 38 are joined at the bottom of theflexible member 26 by a connecting wire portion 40. The provision of thewire portion 40 is not critical and any other means of securing thewires 36 and 38 which prevents the wires from being completely separatedfrom'the flexible member could also be utilized.

Retainingbands 42 enclose the flexible member 26 as well as the wires36, 38 and prevent the latter wires.

from moving transversely outside the grooves. Therefore, although thewires 36, 38 may slide longitudinally within the grooves relative to theflexible member 26,

when the latter flexes, as will be hereinafter described, the wires maynot move outside the grooves. Consequently, the wires 36, 38 remainparallel to each other independently of the flexure of the member 26.The two parallel wires 36, 38, in the absence of twisting of the rod 26about its own axis, always define a single plane.

In the embodiment shown in FIGS. 2 and 3 two parallel wires 36, 38 wereutilized. It is understood that a single wire could also have beenutilized to provide output results. In addition, all four grooves couldbe utilized wherein the wires 36, 38 shown would form one parallel pairlying in a first plane and additional wires would be placed within thegrooves 28, to form a second pair lying in a second plane. Although inthe embodiment shown such two planes would be orthogonally related, suchis not necessary and any intersecting planes could be used. Furthermore,although the wires in a given pair of grooves are shown interconnectedby means of the section 40, each of the wires could independently beattached to the flexible member, and in fact, for some embodiments ofthe deviation sensing means, as will be hereinafter described, separatewires are required.

The principle of operation of the present invention can best beexplained with reference to FIG. 4. When only two oppositely disposedwires 44, 46 are used, the curvature device or transducer is utilized tomeasure curvature in a plane defined by the two wires. In FIG. 4, thelower portion of the rod 48 is shown unflexed. An upper portion of therod is shown flexed about a point 0. The wire 46 has a radius ofcurvature designated by the reference numeral 50 while the wire 44 has aradius of curvature which is equal to the radius of curvature 50 plusthe cross sectional diameter of the rod 48. Consequently, within thecurved arc defined by the angle 6, the length of the wire 46 within thecurved arc is smaller than the length of the wire 44 enclosed by thesame curved arc. Accordingly, the extension 47' relative to the rod 48increases over the initial length of the extension 47 while the lengthof the extension 45' decreases in relation to its original length ofextension 45. Thus, as shown, a given point on wire 44 which, in itsoriginal position coincided with the upper end of the flexible rod 48now represents a point a which is further down along the flexible member48. Similarly, a point 11 which in its original position coincided withthe upper end of the flexible member 48, when flexed, now becomes 12'which is a distance beyond the end of the flexible member 48. Flexingtowards the left instead of the right would increase the length of theextension 45' while decreasing the length of the extension 47' inrelation to the original length when the rod is unflexed.

The change of lengths of the extensions relative to the flexible member,contains information relating to the curvature which the memberexperiences. Thus,

one wire could also be used to sense the curvature change. Two wires,identifying a single plane, senses curvature within that single plane.However, theme of two wires presents a greater measureable deviationfrom the unflexed condition which can provide greater sensitivity ofmeasurement.

Once the sensing transducer detects a change in curvature by means ofthe relative change in position of the unfixed end of the sensing wires,this change in position is then translated into continuous electricalsignals which are proportional to such change in position. Referring nowto FIGS. 5 and 6 one such deviation sensing means for producing anelectrical output proportional to such positional change in sensingwires is shown. In this embodiment a non-conductive elongated flexiblemember 52 in the form of a cylindrical tube has a hollowed central boretherein with longitudinal grooves 56, 58 on opposing outer sidesthereof. A resistive collar 60 is mounted adjacent one end of theflexible member member and anchored fixedly to the flexible member.Opposite edges of the resistive collar are connected respectively towires 62 and 64 which pass through the central bore 54 and lead from theflexible member such that terminals 66, 68 are available across which avoltage supply 70 can be connected.

Conducting sensing wires 72, 74 are located within the grooves and fixedto the flexible member at points 76, 78. The upper ends of each of thewires 72, 74 connect to conductive sliders 80, 82 which reside in thegroove of the core and abut the inner surface of the collar 60. The endsof the wire opposite from that of the sliders are available externallyat the output terminals 84, 86. A measuring device, such as a volt meter88 can be interconnected across the output terminals 84, 86 to measurethe voltage across the conducting sensing wires 72, 74. A variableresistance 90 can be placed across the volt meter 88 to zero the voltmeter 88 at any specific value thereby presetting a reference zerovoltage corresponding to a given referenced amount of curvature.

Referring now to FIG. 6 there is shown an electrical equivalent of theembodiment shown in FIG. 5. It is seen that a voltage V is impressedacross a resistor 92. The resistor 92 represents the resistive collar 60in FIG. 5. Wires 94 and 96 correspond to the longitudinally extendingsensing wires 72, 74 in the embodiment of FIG.,

5. The ends of these wires are respectively connected to sliders 98,which abut the resistance 92. As the sliders 98, 100 are caused to moveapart, a different amount of voltage can be sensed at the outputterminals between the wires 94, 96. The amount of voltage isproportional to the amount of spacing between the sliders 98, 100.Normally, zero voltage would be read when the slider 98 is located atthe same point on the resistor 92 as the slider 100. A maximum voltagewill exist when the slider 98 is at one end of the resistor 92 and theslider 100 is at the opposing end. Any intermediate values will beproportional to the amount of distance the slider'arms are movedrelative to the resistor 92. The output can be read by a volt meter andthe volt meter can be zero adjusted such that for a given distancebetween the sliders 98 and 100 the voltage will read zero and willsubsequently read positive or negative voltage values relative to thatpredetermined referenced zero position. Thus, a given amount ofcurvature can be established as the reference point and all curvaturesgreater or lesser than the reference amount can be read out.

Referring now to FIG. 8 there is shown various methods of interconnetingthe ends of the sensing wires to the resistive collar. In FIG. 8, thenon-conductive flexible member 102 contains the central bore 104 and aresistive collarl06 which has conductive bands 108, which canrespectively be interconnected across I the voltage source through wirescontacting the same (not shown). The conductive wires 112, 114 passthrough grooves 116, 118 respectively, such that they contact the innersurface of the resistive collar 106. In one method shown in conjunctionwith wire 112 a curved portion 119 is formed in the wire and made rigidsuch that it abuts the inner surface of the resistive collar 106 and canslide along each inner surface. In another method, shown in conjunctionwith conductive wire 114 a leaf spring 120 of conductive material isfixedly connected onto the conductive wire 114 and has the outer edgethereof 122 slidably brushing against the inner surface of the resistivecollar 106. In either method, the slide means will be in contact withthe inner surface of the resistive collar and the position of the slidemeans will vary as the curvature of the flexible member 102 changes inthe plane formed by the wires 112, 114.

An alternate approach to providing a deviation sensing means is shown inFIG. 7 wherein resistive wires 124, 126 are utilized. The lower ends ofthese wires are connected to the bottom of the flexible member 128 inany conventional manner. An electrical bridge arrangement is utilizedhaving fixed resistors 130 and 132 forming two arms with a terminalpoint 134 therebetween. Resistive wire 124 is connected at terminalpoint 136 to resistor 132 and similarly resistive wire 126 is connectedat terminal point 138 to resistor 130. Brush slides 140, 142 arerespectively connected at the ends of the conductive wires 124, 126 todetect change in position of the wires as the flexible member is flexed.The ends of the brush slides are connected to ground at 144, which formsthe fourth terminal of the bridge. A voltage source 148 isinterconnected across two opposing terminals 134 and the ground terminal144. An indicator means 146 is connected across the other opposingdiagonal terminals 136, 138. In this manner the resistive wire 124 inconjunction with the brush 140 forms one arm of the bridge and theresistive wire 126 in conjunction with the brush 142 forms the other armof the bridge. The resistance of each of these arms will change as theflexible member is flexed. Such change in resistance unbalances thebridge which unbalance can be read on the indicator 146 whose outputwill be a functional relationship with the amount of curvature caused bythe flexure of the flexible member 128.

Still another approach to detecting the deviation in position of thesensing wires and coverting it to an electrical signal is shown in FIG.9. In this embodiment a potentiometer 150 is mounted on top of theflexible member 152. The potentiometer 150 has a screwhead 154 with aslot or groove 156. Such potentiometers are available and utilized inprinted circuits. The potentiometer adjustment is made by inserting ascrewdriver into the slot 156 and turning the head 154 in one directionor another about the axis of the potentiometer 150. When used with thepresent invention, a fixed connector 158, such as a wire may beconnected to the ends of the sensing wires 160, 162 by any suitablemeans such as for example solder or welds 164. The wire 158 is made topass through the slot 156. Electrical leads 165 of the potentiometer 150are connected to a suitable circuit such as an oscillator or bridgecircuit. When the wires 160 162 change in length, the wire 158 is causedto turn about the axis of the potentiometer 150 and head 154 issimilarly caused to turn. The null position or normal position of thehead 154 is shown in FIG. 9. It is to be noted, that in this embodimentthe sensing wires which extend along the flexible member need not bemade of electrically conductive material. Thus, it would be possible touse an interconnecting wire to fixedly connect the sensing wires to theelongated flexible member as was described in connection with FIG. 3.

In FIG. 10, the curvature sensing device is shown with four wirescontained in four grooves within the flexible member 170. Wires 172 and174 define a first plane which will detect curvature movement withinthat plane. Wires 176 and 178 define a second plane and will detectcurvature within that plane. Although the planes are shown orthogonallyperpendicular they can be intersecting at other angles as was heretoforeexplained. In addition, arbitrary bending of the rod 170 in other planescauses all four wires to change in length. By knowing the components ofcurvature in each of the two major planes, the resulting curvature inany other plane may be ascertained.

Referring now to FIGS. 11 and 12 there is-shown the flexible member 180having the center bore 182 and wherein the grooves 184 are formed with anarrow neck portion 186 at the outer surface. The necks are formed suchthat they can slightly deform and spread apart upon application ofpressure. When inserting the wires, such pressure is placed at thenarrow neck portion to deform it, thereby permitting the wires to entertherein. Once the wires are placed within the grooves they are retainedby the narrow neck and no additional retaining means need be connectedto hold the wires within the grooves. FIG. 11 shows an embodiment havingfour wires while FIG. 12 shows an embodiment containing two wires.

Although heretofore the embodiments have shown the sensing wiresextending longitudinally along the flexible member referring now to FIG.13 there is shown an elongated flexible member 190 containing I wires192 and wires 194 spirally winding about the elongated flexible member.While one wire could be used, similar to using one wire in thelongitudinal embodiment, two wires are shown wherein one is spirallyrotated in a clockwise direction and the other is spirally rotated in acounterclockwise direction using two wires will increase the sensitivityof the device. As is shown, a resistive collar 195 is again used tosense the deviation and convert it to electrical signals. Using'thespiral embodiment, the sensing device will possess rotationalsensitivity and be able to continuously sense the rotational curvatureabout a center axis of the flexible member 190. The sensitivity of theunit will be inversely proportional to the pitch angle of the spiral.

By combining various individual sensing units it is possible to form acascaded measurement sensor of the type shown in FIG. 14 wherein a firstsection shown generally at 200 contains rotational sensitivity by havingspirally wound wires 202, 204 about the flexible member. The secondsection shown generally at 206 has dual axis sensitivity by including afirst pair of wires 208, 210 extending longitudinally in a first planeand a second pair of wires one of which is shown 212 also extendinglongitudinally and lying in a plane perpendicular to the first pair. Athird section shown generally at 214 contains single axis sensitivity byhaving a single pair of wires 216 extending longitudinally along theflexible member and lying in a single plane. Resistive collars 218 areused to sense the deviation of each of the wires as was heretoforeexplained.

In order to utilize the present device either for industrial use onconstruction elementsor material testing elements, or in order toprovide use as a poor posture detector it is necessary to mount theflexible member onto the item being measured. When used as a poorposture detector, belt means can be utilized which secures the sensingdevice against the patients spine. Preferably, the belt means are easilysecured around the patient and readily removed therefrom so that thepatient can make necessary adjustments himself. The deviation sensingmeans could in fact be included within the belt and batteries utilizedto supply the necessary voltage source to make the entire unit portable.

When attaching the curvature sensing device onto an industrial elementbrackets of the form shown in FIG. at 220 could be utilized. Suchbrackets would include mounting holes 222 to firmly attach the flexiblemember 224 to the element being measured. However, the bands 226 shouldnecessarily permit the member 224 to freely pass therein permittingflexure of the member 224 as the element bends and produces a givencurvature.

There has been disclosed heretofore the best embodiments of theinvention presently contemplated. However, it is understood that variouschanges and modifications may be made thereto without departing from thespirit of the invention.

What is claimed is:

l. A curvature measurement device comprising an elongated flexiblemember, at least one pair of substantially parallel sensing wiresextending longitudinally along said member, the wires of said at leastone pair being disposed on opposing sides of said member and togetherdefining a plane, said member including retaining means for maintainingsaid wires substantially coextensive with said member along the lengthsthereof and each of said wires of said at least one pair being fixedlyconnected at one end thereof to said member and having the other endthereof free for longitudinal displacement along said member within saidplane, whereby flexing of said member within said plane causes the freeends of said at least one pair of sensing wires to be displaced relativeto each other in opposing directions along said member; and deviationmeans coupled to said free ends for producing an electrical signalproportional to the change of relative longitudinal positions of saidfree ends of a respective pair of sensing wires to thereby provide ameasure of curvature within the respective plane.

2. A device as in claim 1 and comprising two pairs of sensing wires eachwire extending longitudinally along said member, each pair defining adifferent plane, and

each pair measuring the curvature within its defined .plane.

3. A device as in claim 2 and wherein said planes are orthogonallyperpendicular.

4. A device as in claim 1 and wherein said deviation sensing meanscomprises resistive means fixedly located on said member at said otherlocation and adapted to have a voltage impressed across it, and whereinsaid sensing wires are conductive and include sliding means electricallycontacting said resistive means whereby said electrical signal is thevoltage between said wires.

5. A device as in claim 4 and wherein said resistive means comprises aresistive collar surrounding said flexible member and wherein saidflexible member is a non-conductive cylindrical member.

6. A device as in claim 5 and wherein said sliding means comprisesconductive spring means brushing said resistive collar.

7. A device as in claim 5 and wherein said sliding means comprises acurved section of said Wire in sweeping contact with said resistivecollar.

8. A device as in claim 5 and further comprising feed wires connected tosaid resistive collar and wherein said flexible member includes a hollowbore therein, said feed wires passing through said hollow bore to saidcollar.

9. A device as in claim 1 and wherein said wires are electricalresistance wires and wherein said deviation sensing means comprises anelectrical bridge circuit having four arms with two pairs of opposingdiagonals, a voltage source adapted to be connected across one pair ofdiagonals, a voltage sensing device adapted to be connected across theother pair of diagonals, first and second resistance means connectedrespectively in two adjacent arms, and two sliding contact meansrespectively contacting said two resistance wires at said otherlocations, said wires and their respective sliding contact meansconnected respectively in the two remaining arms.

10. A device as inclaim l and wherein said retaining means compriseslongitudinal grooves in said flexible member in which each of said wiresrespectively extend.

11. A device as in claim 10 and wherein said grooves contain a narrowneck portion at the outer edge thereof such that said wires snap intosaid groove and are retained therein.

12. A device as in claim 10 and wherein said retaining means comprises aplurality of holding means retaining said wires in said grooves.

13. A device as in claim 1 and further comprising audio means responsiveto said electrical signal whose frequency is proportional to saidelectrical signal.

14. A device as in claim 1 and further comprising audio means whoseamplitude is proportional to said electrical signal.

l5.'A device as in claim 1 and further comprising readout meansproviding a visual signal proportional to said electrical signal. i

. 16. A device as in claim 1 and further comprising means forestablishing a reference signal such that said electrical signal willrepresent a deviation from said reference signal.

17. A device as in claim 1 and wherein said flexible member comprises aplurality of cascaded sections each section measuring the curvatureabout at least one axis.

18. A device as in claim 1 and wherein said flexible member furthercomprises mounting means adapted to interconnect said flexible member toan object being measured.

19. A curvature measurement device comprising an elongated flexiblemember; two sensing wires spirally extending along said flexible memberin opposing rotational directions, said member including retaining meansfor maintaining said wires substantially coextensive with said memberalong the lengths thereof and each of said wires being fixedly connectedat one end thereof to said member and having the other end thereof freefor substantially axial displacement along said member, wherebyrotational flexing of said member about the central axis thereof causesthe free ends ends of said pair of sensing wires to thereby provide ameasure of the rotational curvature about the central axis of saidmember.

1. A curvature measurement device comprising an elongated flexiblemember, at least one pair of substantially parallel sensing wiresextending longitudinally along said member, the wires of said at leastone pair being disposed on opposing sides of said member and togetherdefining a plane, said member including retaining means for maintainingsaid wires substantially coextensive with said member along the lengthsthereof and each of said wires of said at least one pair being fixedlyconnected at one end thereof to said member and having the other endthereof free for longitudinal displacement along said member within saidplane, whereby flexing of said member within said plane causes the freeends of said at least one pair of sensing wires to be displaced relativeto each other in opposing directions along said member; and deviationmeans coupled to said free ends for producing an electrical signalproportional to the change of relative longitudinal positions of saidfree ends of a respective pair of sensing wires to thereby provide ameasure of curvature within the respective plane.
 2. A device as inclaim 1 and comprising two pairs of sensing wires each wire extendinglongitudinally along said member, each pair defining a different plane,and each pair measuring the curvature within its defined plane.
 3. Adevice as in claim 2 and wherein said planes are orthogonallyperpendicular.
 4. A device as in claim 1 and wherein said deviationsensing means comprises resistive means fixedly located on said memberat said other location and adapted to have a voltage impressed acrossit, and wherein said sensing wires are conductive and include slidingmeans electrically contacting said resistive means whereby saidelectrical signal is the voltage between said wires.
 5. A device as inclaim 4 and wherein said resistive means comprises a resistive collarsurrounding said flexible member and wherein said flexible member is anon-conductive cylindrical member.
 6. A device as in claim 5 and whereinsaid sliding means comPrises conductive spring means brushing saidresistive collar.
 7. A device as in claim 5 and wherein said slidingmeans comprises a curved section of said wire in sweeping contact withsaid resistive collar.
 8. A device as in claim 5 and further comprisingfeed wires connected to said resistive collar and wherein said flexiblemember includes a hollow bore therein, said feed wires passing throughsaid hollow bore to said collar.
 9. A device as in claim 1 and whereinsaid wires are electrical resistance wires and wherein said deviationsensing means comprises an electrical bridge circuit having four armswith two pairs of opposing diagonals, a voltage source adapted to beconnected across one pair of diagonals, a voltage sensing device adaptedto be connected across the other pair of diagonals, first and secondresistance means connected respectively in two adjacent arms, and twosliding contact means respectively contacting said two resistance wiresat said other locations, said wires and their respective sliding contactmeans connected respectively in the two remaining arms.
 10. A device asin claim 1 and wherein said retaining means comprises longitudinalgrooves in said flexible member in which each of said wires respectivelyextend.
 11. A device as in claim 10 and wherein said grooves contain anarrow neck portion at the outer edge thereof such that said wires snapinto said groove and are retained therein.
 12. A device as in claim 10and wherein said retaining means comprises a plurality of holding meansretaining said wires in said grooves.
 13. A device as in claim 1 andfurther comprising audio means responsive to said electrical signalwhose frequency is proportional to said electrical signal.
 14. A deviceas in claim 1 and further comprising audio means whose amplitude isproportional to said electrical signal.
 15. A device as in claim 1 andfurther comprising readout means providing a visual signal proportionalto said electrical signal.
 16. A device as in claim 1 and furthercomprising means for establishing a reference signal such that saidelectrical signal will represent a deviation from said reference signal.17. A device as in claim 1 and wherein said flexible member comprises aplurality of cascaded sections each section measuring the curvatureabout at least one axis.
 18. A device as in claim 1 and wherein saidflexible member further comprises mounting means adapted to interconnectsaid flexible member to an object being measured.
 19. A curvaturemeasurement device comprising an elongated flexible member; two sensingwires spirally extending along said flexible member in opposingrotational directions, said member including retaining means formaintaining said wires substantially coextensive with said member alongthe lengths thereof and each of said wires being fixedly connected atone end thereof to said member and having the other end thereof free forsubstantially axial displacement along said member, whereby rotationalflexing of said member about the central axis thereof causes the freeends of said sensing wires to be displaced relative to each other alongsaid member; and deviation means coupled to said free ends for producingan electrical signal proportional to the change of relative positions ofsaid free ends of said pair of sensing wires to thereby provide ameasure of the rotational curvature about the central axis of saidmember.